Field of the Invention
The present invention relates to an exhaust gas purification filter, an exhaust gas purifier, and a method of using the exhaust gas purifier. More particularly, the present invention relates to the exhaust gas purification filter capable of properly purifying NOX in exhaust gas even during the regeneration of the filter, suppressing an increase in pressure loss, and including a surface trapping layer with appropriate durability, the exhaust gas purifier, and the method of using an exhaust gas purifier.
Description of the Related Art
In order to purify exhaust gas emitted from a diesel engine or the like, a plurality of filters are disposed in an exhaust path of the engine. As the filters, there are a diesel particulate filter (DPF), an SCR catalyst (a catalyst for selectively reducing components to be purified through a reduction reaction) filter disposed on the downstream side of the DPF, and the like. In addition, the DPF primarily traps particulate matter (PM) containing soot in the exhaust gas and prevents the particulate matter from being emitted to the air. An SCR catalyst converter reduces NOX in the exhaust gas using ammonia (NH3) generated by decomposition of urea injected from a urea injector disposed on the upstream side thereof.
The DPF typically includes a catalyst loaded therein, which contains a precious metal, for the purpose of oxidizing and removing carbon monoxide (CO) and hydrocarbons (HC), and the like. That is, the DPF burns off and removes soot accumulated therein every predetermined period (combustion regeneration process). At this time, the combustion of the soot is accelerated by the catalyst. In addition, carbon monoxide (CO) and hydrocarbons (HC) generated by the decomposition of the soot during the combustion of the soot are oxidized and removed by the catalyst.
In addition, there may be cases where a trapping layer (surface trapping layer) for trapping the PM is disposed on the surface of a partition wall of the DPF (refer to Patent Document 1). In addition, in the DPF, the PM is prevented from penetrating into the porous partition wall and blocking the pores of the partition wall by the surface trapping layer. When the pores of the partition wall are blocked, there is a problem in that pressure loss is rapidly increased.
[Patent Document 1] Japan Patent No. 5616059